1. Field of the Invention
The present invention relates to a radio controlled model apparatus, a controller for a radio controlled model apparatus, and a frequency hopping pattern selection method. Particularly, the present invention relates to a radio controlled model apparatus and a controller for a radio controlled model apparatus, each of which uses frequency hopping spread spectrum communication, and to a frequency hopping pattern selection method used in radio frequency hopping spread spectrum communication.
2. Description of the Prior Art
The use of the spread spectrum radio technique for wireless control of radio controlled model apparatuses, such as model airplanes, has now become widespread. The 2.4 GHz band is commonly used in the spread spectrum radio technique. The spread spectrum radio technique involves either a frequency hopping spread spectrum system or a direct sequence spread spectrum system. To use the entire given frequency range at the same time, the direct sequence spread spectrum system is a communication method which does not perform channel separation. In contrast, the frequency hopping spread spectrum system is a communication method which uses ten or more frequencies obtained through time division mapping by employing a specific algorithm. In Japan, for example, the frequencies are obtained by shifting the 26 MHz band by 1 MHz. A variety of frequency hopping patterns can be created using the algorithm. When the frequency hopping spread spectrum system is applied to radio controlled model apparatuses, one frequency hopping pattern is used to communicate between a transmitter and a receiver included in model aircraft including model airplanes, helicopters, airships, dragonflies, and so on. The apparatus incorporates the transmitter as a part of the controller that functions as a radio parent station for the radio controlled model apparatus, and the receiver that functions as a radio mobile station for the apparatus. The communication path, created using a single frequency hopping pattern, is referred to hereinafter as a radio zone.
In order to facilitate the understanding of the technical content to be described hereinafter, the whole configuration of a radio controlled model apparatus will be briefly explained here. The radio controlled model apparatus includes a controller, or control device, which functions as a radio parent station, and the controller comprises a transmitter and an operation unit. The transmitter, which transmits control information to a model aircraft for example, employs the frequency hopping spread spectrum system when transmitting radio waves. The operation unit has a wheel or joystick for controlling a model aircraft. The transmitter and the operation unit are normally integrated into a single, portable device. The integrated device is referred to as a controller, or control device.
The power transmission unit has a different configuration depending on the type of model aircraft, including model airplanes, helicopters, airships, and so on. The power source may be a fuel engine or an electric motor depending on the type of model aircraft. A different mechanism may be used for directional control and speed control depending on the type of model aircraft. Generally, the aircraft is provided with a receiver, servos, motors for driving rudders attached, for example, to a horizontal stabilizer and a vertical fin in a model airplane, amplifiers for supplying power to motors, and a frame for carrying them. In the above configuration, the receiver receives radio waves from the controller and sends the necessary control information to the servos. The amplifier receives the signals from the servos to operate the motors.
In the radio controlled model apparatus with the above configuration, the same radio zone is shared by a single controller and a single model aircraft, while other radio zones are shared by other controllers and their respective model aircraft. Thus, different frequency hopping patterns, independent of each other, are used. A different frequency hopping pattern is used for each radio zone. A specific controller can thereby control a specific aircraft without radio signal interference from another radio zone, even if the controller's radio zone is overlapped by a neighboring radio zone. A neighboring radio zone refers to a different radio zone, whose hopping pattern results in the temporary sharing of a particular radio frequency. One such radio controlled model apparatus is disclosed in Japanese Patent Publication No. 10-252884, the contents of which are hereby incorporated by reference.